不同Ce/Mn摩尔比对CeO_2-MnO_x催化剂低温NH_3选择性催化还原NO的影响

以高锰酸钾和硝酸锰为锰源,采用改进的共沉淀法制备了不同Ce/Mn摩尔比的Ce O2-Mn Ox催化剂.以NH3为还原剂,考察了催化剂低温(小于150℃)NH3选择性催化还原NO的性能.并采用XRD,BET,H2-TPR,NH3-TPD和XPS等手段对催化剂的物理化学性质进行表征.结果表明,Ce O2-Mn Ox催化剂在50~150℃温度区间内表现出了良好的催化活性.引入适量的Ce可以有效地改变催化剂的晶粒大小,增强其氧化还原能力;而Mn的加入,促进了其低温SCR活性.当Ce/Mn摩尔比为1∶3时(C1M3),低温活性最佳,在82~150℃温度区间内NO去除率达到90%以上,这主要是由于C1M3催化剂有较高含量的表面吸附氧、大量的弱酸性位点、良好的氧化还原性能以及表面较高含量的Mn4+物种.

Effect of Ce/Mn Molar Ratios on the Low-Temperature Catalytic Activity of CeO2-MnOx Catalyst for Selective Catalytic Reduction of NO by NH3

CeO2-MnOx catalysts were prepared by improved co-precipitation method using potassium permanganate and manganese nitrate as manganese sources, and the effect of different Ce/Mn molar ratio on the SCR performance was investigated. The catalysts were characterized by XRD, BET, H2-TPR, NH3-TPD and XPS. The results indicated that the CeO2-MnOx catslysts exhibited the excellent catalytic activity at 50-150 oC. The crystal sizes and redox properties of CeO2-MnOx catalysts were dramatically affected with the addition of Ce speices, and the introduction of Mn species could contribute to the low-temperature catalytic activity. When the Ce/Mn molar ratio was 1:3 (C1M3), the C1M3 catalyst showed the best catalytic activity and above 90% NO conversion was obtained at 82-150 oC. The excellent SCR activity of C1M3 was attributed to its higher surface oxygen species, its excellent redox property, its abundant weak acid sites and its higher surface Mn4+ species, which were dependent on the Ce/Mn malor ratios.